The XLR out on the DT provides a transformer tapped direct out with cabinet simulation.

Here are some questions I have, maybe someone can answer them...

- does transformer tapped mean they are pulling the same audio that is going to the speaker including power section distortion just at a much lower level straight from the output transformer?

- how is cab sim applied? Does that signal then go back into the DT for processing to add the cab sim?

- if I am already using cab sims with my amp/preamp modeling, why would I want another cab sim applied to the output here?

- if it is the same type of cab sim as with the amp/pre, what cab are they using? what mic are they using?

- is it linked to the internal amp models stored or to the one being used from the POD?

- can the cab sim be adjusted or changed with an external editor in any way?

I don't think I have solid answers, but I can describe my view of how it may work ... (I have not done any of it)

I don't know what transformer tapped really means, except that it is supposed to emulate power amp tone characteristics on the DT XLR out. I think there is no crisper definition of what it actually does within the DT to achieve this.

Cab sim within the DT is most likely done by the DSP and due to cost of additional AD/DA conversion of a transformer tapped analog signal it will most likely be done before the DA conversion of the signal fed to the power amp section (similar to how reverb in the DT is handled, i,e., before the effect loop out (again to save a DA/AD conversion)). Best case scenario would be if there are 2 DAs after a split of the digital signal path: One going to power amp section and the other going to a DSP cab/mic sim stage before being converted to analog for XLR out. Whether the 'transformer tapping' ends up getting mixed in by the DSP (would required some AD of transformer tapped signal) or in the analog domain is an open question.

Cab / Mic sim is just just a form of EQ / compression combo characterized for a specific Cab/Mic selection. Use it if you like the effect. Even Line 6 seems to have opted for turning Cab sim on in the DT preamp section even though they clearly send the output primarily to the DT speakers. Obviously they could play some more tricks in the DT to compensate for the DT speaker. Would be hard to verify, I think.

Don't know what they did before the latest DT FW update. Now I believe they describe it in the DT MIDI specification, but I did not recheck.

The Cab sim selected in the HD is done by the HD DSP; the cab sim in the DT for the XLR out is done in the DT DSP, I think. They could be aware of each other, but there is no documentation saying so as far as I know.

There are DT MIDI editor SW programs (search forum, i don't recall details) and you can use any generic MIDI control surface/device to control the Cab/Mic setting for the 8 program slots in the DT (once they are programmed the Type sector on the DT is used to select the program (together with the amp type) on channels A and B.

thanks but none of those actually answer the questions. Unfortunately there is no documentation of this feature and there are a lot of issues with the XLR out from the DT. I appreciate your input though...

thanks Phil, kind of what I suspected but just not really diggin why they do it this way. I start with a digital modeled amp and cab, send it through an analog tube amp and then back into the digits to get a second cab makeover and back AGAIN to a usable audio signal to the board... so I guess the DT knows what cab setting I have in the POD and then uses the same cab/mic config in the DT to process my signal a second time... Wow... so what happens if I have no cab selected in the POD? Hmmmm... Why can't it just go from the transformer tap to the XLR without another digital makeover?

Essentially, yes. So what it means is that it's not simply the preamp signal with cab emulation. You get the power amp interaction as well.

Yes, the cab emulation is added post this signal.

This is NOT what Line6 support says. Below is a conversation I had with Line6Hugo (hmerida) about cab modelling, and LVM. Hope it provides some information on Line6's stance. Bear in mind that I asked basically these questions in a different support ticket, and some of the answers I got there do NOT agree with this info. So I think Line6 themselves have different answers depending on who you ask... Professional, eh?

Anyway:

Line6Hugo: When connected via L6 LINK, the cab model in the DT25 is simply being controlled by the HD500 User Interface. Using the default cab models (the ones which automatically pair with the preamp) should provide the same results when using the same preamp and default cab model in the DT25 stand alone.

Me: "In your explanation, the cab modeling is placed before the power amp, not after. Is this really the case, and if so, why is that? It makes much more sense to have it afterwards. Also, why is there cab modeling active in the dt25 standalone when it has a cab and speaker anyway?"

Line6Hugo: - Cab modeling exists in the DT25 to create a complete amp tone. If you prefer to turn it off you may do just that with a connected HD500 or in standalone mode when connected to a MIDI controller accessing the DT25 2.0 firmware features. Having the cab modeling before the power amp in the DT amps ensures a consistent experience when using with or without a POD HD device.

Me: "How does the use of LVM mode and the direct out affect the placement and operation of cab modeling?"

Line6Hugo: - LVM has no impact on the cab modeling. Direct out uses the same cabinet model through a model of the mic’ed DT25 cabinet. This provides a tone which matches the cab model that comes through the DT25 speaker through a mic, as you would here in a recording or through the PA… essentially the same experience you would get with a microphone but direct via XLR.

Me: "Finally, I notice a large difference on the B channel when I activate LVM. My test case is as follows: dt25 a and b channels set with all knobs to 12oclock, topology 2, P-75 Pre (no cab) I have a footswitch set to toggle the amp block on and off and they sound similar (but far from identical). However, if I engage LVM and toggle the amp block on and off, the B channel now sounds very different (much more distorted). Why is this, nothing in your explanation suggests why the power amp/LVM would behave differently."

Line6Hugo: - More information is required to properly answer this question – normally toggling an amp model bypass (on a connected HD500) also toggles the amp between channels A and B. If channel B is not set identically to the amp model when active, the sounds will be different. Also, each channel (if switching) must have its topology settings set identically. Engaging LVM does two things: uses HD Technology to deliver the preamp and power amp modeling (whereas non-LVM provides just the preamp model) as well as scales the level of the Master Volume knob on the DT25.

Some more conversations with support. might be of interest:

From 'afisher'

Hello,

With the DT in LVM and using the direct out, disabling the cab modeling on the HD500 will remove the cab modeling from the output of the DT.

Removing the cab modeling causes the mic modeling to be removed as well.

We tested this scenario here and our ears told us there was no perceived change in tone when changing mic models while the cab modeling is disabled. Thus, the mic modeling does nothing when no cab is being modeled.

I start with a digital modeled amp and cab, send it through an analog tube amp and then back into the digits to get a second cab makeover and back AGAIN to a usable audio signal to the board... so I guess the DT knows what cab setting I have in the POD and then uses the same cab/mic config in the DT to process my signal a second time

As far as I understand it (not far!), there is no audio going back to the pod. The cab modelling is applied at/after the PREAMP stage only.

thanks for all that! as usual, they really don't know what the hell is going on because they will not release a simple block diagram of the actual signal path. It is impossible for the cab modeling to be applied before the power section because it is already being applied there! They are most certainly applying it a second time to the transformer tapped signal or there would be absolutely no need to mention it at all. The only way that can happen is for that signal to be routed back in to the DT to have the cab modeling applied prior to hitting the XLR out. From what I gather from all this discussion is the L6 signal tells the DT which cab is being used in the POD and the DT applies that cab model to the signal.

Line6Hugo: - LVM has no impact on the cab modeling. Direct out uses the same cabinet model through a model of the mic’ed DT25 cabinet. This provides a tone which matches the cab model that comes through the DT25 speaker through a mic, as you would hear in a recording or through the PA… essentially the same experience you would get with a microphone but direct via XLR.

So this kind of makes sense. I have to picture this XLR out as representing a mic placed in front of my cab/speaker so even though the tone coming from my cab/speaker is being created with a modeled amp and cab sim, the mic would capture a second physical cab effect and that is what they are trying to recreate.

This is NOT what Line6 support says. Below is a conversation I had with Line6Hugo (hmerida) about cab modelling, and LVM. Hope it provides some information on Line6's stance. Bear in mind that I asked basically these questions in a different support ticket, and some of the answers I got there do NOT agree with this info. So I think Line6 themselves have different answers depending on who you ask... Professional, eh?

I don't believe I said anything that contradicted what Hugo said there. You asked specifically about LVM. I was answering as if the DT was in regular power mode.

I meant that some other line 6 supporter gave contradictory info. Unfortunatel' they seem to have deleted that ticket, I can't find the conversation. My point is that the line 6 support guys give hazy, ill-defined answers because they don't actually know any better imho. I pressed them really hard for a signal chain block diagram, but 'the display on the pod shows the signal' was the best I got from them. Gah!

Radatats: line6 were adamant that no audio goes from the dt to the pod. The dt can do the cab modelling. It makes sense to me to do it while the signal is still digital, and not after the power amp, even if thats where it should be done for most realistic effect. Why don't you think its done earlier in the chain?

Radatats: line6 were adamant that no audio goes from the dt to the pod. The dt can do the cab modelling. It makes sense to me to do it while the signal is still digital, and not after the power amp, even if thats where it should be done for most realistic effect. Why don't you think its done earlier in the chain?

I am not saying anything goes back to the POD from the DT. But you are missing the point here. The signal is created in the POD with modeled amp and cab/mic sim applied. This is then sent to the DT power section. At the output transformer the main signal is sent to the speaker and another signal is tapped off for the direct out. That tapped signal is what is routed back in to the DT to have the cab sim applied based on what model is selected in the POD and then sent to the XLR. It never goes back to the POD. This signal now imitates the signal that a mic placed in front of your cab would pick up and is available to send to the mixer for your PA.

If it was done earlier in the chain it would not be able to capture the tube power section flavoring. I guess my biggest gripe was the weak signal but it is what it is... I can deal with it now I really understand it.

They state that it is! Its a CAB SIMULATED DIRECT OUT! the cab sim imitates the physical speaker. two paths out of the transformer, one to a real speaker, the other to a cab sim (speaker replacement)...

I am in innovine's camp. Nowhere does it say the Cab sim is applied to the transformer tapped signal directed to the XLR out. It is much more likely (less DA/AD converters are needed) that the Cab sim is happening in the tail end of the preamp model, i.e., in the HD when an Amp is selected and L6 Link is used, or in the DT if you come in with a guitar or via Channel B when no Amp is selected in the HD.Another indicator why this is likely is that both Master Volume and Reverb are applied BEFORE the DT effects loop, i.e., the analog signal coming back from the effects loop is probably not converted back to the digital domain to do an extra Cab and Mic modeling step. If the extra AD/DAs would exist, it would make a lot more sense that reverb and master volume would also be done after the effects loop.Obviously we're all just guessing with spotty and conflicting feedback from several sources and probably no real measurement data we acquired ourselves.Martin

They state that it is! Its a CAB SIMULATED DIRECT OUT! the cab sim imitates the physical speaker. two paths out of the transformer, one to a real speaker, the other to a cab sim (speaker replacement)...

Yeah, I think you're right. I think perhaps we need to step back and kind of look at the bigger picture again. Remember that the DT amp itself contain all the amp and cab modeling that the POD HD does, for starters. When you use L6 Link with the DT in full volume mode, no modeling is being done in the DT itself, except for what happens to the XLR out. You have the preamp signal coming through L6 Link, it hit the power section of the amp in whatever way it configured, goes to the output transformer and out the speaker. The signal going to the XLR out would have cab and mic modeling applied in the DT amp itself before it leaves the amp. This is essentially having two layers of cab modeling if you have the Cab on in the preset in the POD, but, really, you have that with the real cab, too. In the combo or stack power amp modes, the cab modeling from the POD is more re-voiced, anyway. It's really more like an EQ applied to the signal to give the flavor of the amp being modeled.

In LVM, nothing changes on the POD side. The DT, however, bypasses all the topology, class, and other settings associated with the real power amp. Those settings still affect the sound, but the power amp is now being modeled. So you have the POD providing the pre side of the modeling and the DT providing the power amp modeling. Hugo said the cab model doesn't change on the XLR out, and that makes sense. That doesn't mean the output would sound the same, though. It might be very close, but it should be a little different because in full power mode, the signal going to it is going through the real power amp, and in LVM it's going through the modeled power amp. In either case, there's another lay of cab modeling applied to it. The signal is still tapped off the output transformer whether the amp is full or LVM.

This is at least how I understand it to work. I'm, of course, open to correction.

Has anyone tested the difference in the DI out from the DT while changing cab choices in the HD? Or turning the cab selection to "none" in the HD? I would guess, that if what L6Hugo said, unless it defaults to some other cab sim, that if you choose none in the HD for the cab choice that the XLR out from the DT should sound horrible, as it does when you take the XLR off the HD while in combo/stack modes.

, but the power amp is now being modeled. So you have the POD providing the pre side of the modeling and the DT providing the power amp modeling...because in full power mode, the signal going to it is going through the real power amp, and in LVM it's going through the modeled power amp.
.

Well, the signal is always going through the power amp, since its loud and coming out the speaker. My asumption for how lvm works is that a dist is applied digitally, after the preamp (possibly after the loop) to fake a driven power amp, and then it's reduced in volume to give lvm mode, and then goes into the power section which runs pretty clean. The tap on the transformer goes to the xlr out and the full windings power the speaker.

Pull the Master Volume knob on DT50, or use the switch on the back of DT25 to toggle the Low Volume Mode “On.” Low Volume Mode functions independently of POD HD and significantly lowers the overall DT amplifier’s volume level. Way beyond a traditional master volume, Low Volume Mode lets you take your DT amp down to whisper-quiet levels for recording or late-night jamming. Since tubes distort less at low volumes, Low Volume Mode utilizes HD technology to pick up the slack and fill out the tone with rich power amp modeling so it still feels and sounds like it’s cranked up even at low levels (Also see the Direct Out functionality on page 4•6.)

So LVM configures the DT power section to either be all tube (off) or adds power amp modeling (on) to the L6 signal prior to hitting the tubes. Either way, it does not affect or change anything in the POD, just how it acts upon the signal it gets from the POD.

Here it gets confusing again...

D Direct Out

The DT amplifier’s DIRECT OUT continues to function as an analog output with L6 LINK in use. Use of this XLR output is recommended to feed your “fully baked” POD HD + DT amp tone to an external recorder, mixing console, etc. Since the audio signal fed to the DT amp via L6 LINK is a mono signal, this Direct Out is a mono signal as well. Note that the Direct Out functionality differs based on the DT amp’s LOW VOLUME MODE (see page 4•3) and STANDBY switch settings:

• Low Volume Mode On, Amp in Standby = Direct Out signal consists of the “Full” (preamp + power amp) Amp Model with no analog amp. This is a handy option for “silent recording” while still providing the tone of a cranked amp.

This description makes sense if you consider the DT as standalone but not if you are using L6 link. LVM does not change what is coming from the POD so your pre or full amp is dependent on your patch, not the LVM switch. They also fail to address the cab sim part for the direct out again...

This description makes sense if you consider the DT as standalone but not if you are using L6 link. LVM does not change what is coming from the POD so your pre or full amp is dependent on your patch, not the LVM switch. They also fail to address the cab sim part for the direct out again...

Well, the cab sim remains the same whether you're in LVM or full power mode. The cab and mic applied to the output will just be the same as whatever you have selected in the preset on the POD.

Where does it actually say that Cab modelling is done in the DT when L6 Link is used. I though having read it, but I can't find it anymore.

I have no dout that Cab modelling is an option when the DT preamp models are used because at least the MIDI guide says so (and there may be other statements in the user doc).

Maybe we're chasing a ghost (Cab modeling) and the DT's really only factor a real power amp signal distortion into the XLR out signal when the DT preamp models are not used?

That could be a possibility as well, I suppose. Although, I think I was just assuming that since the DT is capable of applying cab and mic modeling on the output on its own, it should be fully capable of doing it with the POD attached, too.

I guess my question is why does all this matter? Is there something you're trying to do that's not working the way you want? Or is it just curiosity about how everything works? Frankly, Line 6 has never been all that great about giving answers to these sort of "sausage-making" questions. I think they just assume most people don't want or need to know. I understand how it's frustrating to some people.

Frankly, Line 6 has never been all that great about giving answers to these sort of "sausage-making" questions. I think they just assume most people don't want or need to know. I understand how it's frustrating to some people.

"if it sounds good it is good" seems to be their philosophy, but i wonder if the signal chain is such a mess that they can't reveal it cos it would damage their product credibility. When you start to read threads like this you start to wonder how its possible to create such confusion about something which should be pretty straigtforward. something smells with the whole thing. And besides, "if it sounds good it is good" doesnt help when things dont sound good.

Frankly, Line 6 has never been all that great about giving answers to these sort of "sausage-making" questions. I think they just assume most people don't want or need to know. I understand how it's frustrating to some people.

you nailed it!

"if it sounds good it is good" seems to be their philosophy, but i wonder if the signal chain is such a mess that they can't reveal it cos it would damage their product credibility. When you start to read threads like this you start to wonder how its possible to create such confusion about something which should be pretty straigtforward. something smells with the whole thing. And besides, "if it sounds good it is good" doesnt help when things dont sound good.

Just for the heck of it I ran that XLR Direct Out from my DT50 Head (using LVM) into the Mic input of my HD500 turned the mic pot all the way up and then proceeded to make a few stereo patches using Amp Models and effects and recorded some tracks with Audacity to my hard drive, (I know there are better programs out there). With very minimal tweaking I had some very good quality sound tracks. It surprised me as I'm really always learning with this stuff. I was just amazed at how full the tracks sounded. I recorded silently monitoring from the pod with Beyerdynamic DT990 (600 Ohm) headphones and the monitored sound was identical to the recorded sound, IMO.

Seems that this is not ideal for ANY setup that uses different power amp configurations because volume balanced DT output requires up to 19dB variation of levels sent from the POD, i.e., theDI output would move around in 4x loudness range. Maybe i did not get this right, but that seems to be the conclusion from the above email ;-(.

After emailing tech support numerous times regarding the DI I got this, and I was NOT happy.

"Unfortunately on DT25 amp the Master Vol on the DT25 does not control DI at all. The DI is controlled by the output of the modeling amps used on the POD. Sorry if this isn't ideal for your set up."

Is this referring to using the DT25 in LVM or normal mode? Or both? I spent a little time messing around with this over the weekend, and it certainly seemed to me that the DT25's master volume controlled the volume of the DI.

Is this referring to using the DT25 in LVM or normal mode? Or both? I spent a little time messing around with this over the weekend, and it certainly seemed to me that the DT25's master volume controlled the volume of the DI.

Confirmed in LVM. Here's my problem and I'm desperate for help.

If I set up 4 identical patches:A,B,C,and D and set A to an amp that uses Voice I on the DT, set B for a Voice II model, C-III, D-IV and then I adjust those patches so that the volume is consistent as I listen to the speaker (only using the model's gain and channel volume [see system settings]), when I monitor those same patches through a mixer board feed of the DT's DI - the patch using Voicing III is way low, like half the volume, of the other three patches/voices. But the patches also are level when I listen through the POD's headphone out.

So:
level coming out of the speaker
level coming out of the POD headphone out
NOT level coming out of the DI

As you might guess, if I set the patches' levels using just the DI as a monitor, patch voicing 3 is now twice as loud when played back with the speaker.

I need to know how to set my DT Dream Rig so that patches using models employing different amp voicings are level across both the speaker and the DI of the DT.

I just hope it's something tweakable and not an amp failure issue as I have had problems with this amp before... I'm going to experiment to see if I can reproduce this in full vol mode with preamp models.

System settings: (for all patches)

Input 1: guitar+variax

Input 2: variax

Mixer block:

Path A +0dB center panned

Path B mute

I also set every single patch to Class A/B Pentode and an identical JTV setting.

If I set up 4 identical patches:A,B,C,and D and set A to an amp that uses Voice I on the DT, set B for a Voice II model, C-III, D-IV and then I adjust those patches so that the volume is consistent as I listen to the speaker (only using the model's gain and channel volume [see system settings]), when I monitor those same patches through a mixer board feed of the DT's DI - the patch using Voicing III is way low, like half the volume, of the other three patches/voices. But the patches also are level when I listen through the POD's headphone out.

So:
level coming out of the speaker
level coming out of the POD headphone out
NOT level coming out of the DI

As you might guess, if I set the patches' levels using just the DI as a monitor, patch voicing 3 is now twice as loud when played back with the speaker.

I need to know how to set my DT Dream Rig so that patches using models employing different amp voicings are level across both the speaker and the DI of the DT.

I just hope it's something tweakable and not an amp failure issue as I have had problems with this amp before... I'm going to experiment to see if I can reproduce this in full vol mode with preamp models.

System settings: (for all patches)

Input 1: guitar+variax

Input 2: variax

Mixer block:

Path A +0dB center panned

Path B mute

I also set every single patch to Class A/B Pentode and an identical JTV setting.

POD mstr vol: 75%

DT mstr vol: 75%

JTV/VDI>PODHD500/L6>DT-25

In LVM mode, yes, the DT's master volume has no effect on the direct out because of the way the tube power section is interacting with the direct out (in LVM, it isn't - the direct out is getting an emulated power amp signal from the processor). In full volume mode, the direct out is getting a signal that's tapped off the power transformer, so that is being affected by the master volume.

In LVM mode, yes, the DT's master volume has no effect on the direct out because of the way the tube power section is interacting with the direct out (in LVM, it isn't - the direct out is getting an emulated power amp signal from the processor). In full volume mode, the direct out is getting a signal that's tapped off the power transformer, so that is being affected by the master volume.

Is there are a reason you're using LVM?

"Is there are a reason you're using LVM?" -wife and two kids.

Seriously, At home LVM allows me to tinker with patches and sounds while monitoring with headphones. You can't get a good read on your D.I. sound while the speaker is rattling the room. My neighbors and family definitely don't want to hear test loops being cranked for an hour while tweaking patches. Live it allows you to get a good read on your signal to the board before you switch standby on and work on your stage volume. And sometimes I play gigs where full vol is just too loud. I prefer to play full vol with pre's because it sounds glorious, but I'm stuck with LVM because all reasons above.

If the DI worked in standy for full vol., I would use it a LOT more. (huge bummer there)

I get the over-view of the DI schematic. This thread covered that pretty thoroughly. My question is:

Since I have the Master vol set identically on the DT and the POD and I level my selection of patches using the speaker on the DT, why is my DI level NOT level?

I'll admit that after more testing, the volume level discrepancy I mentioned does not seem to be an issue in Full volume mode with preamp models. But that still does me no good when I'm in LVM.

I got this from Line6 tech support today:

"The DI from the amp will never match the speaker or the headphones because it does not have it's own gain adjustments (i.e. chan volume on amp and master volume on Pod) I would recommend using the DI from the POD for a better match."

Except they should know that when you're connected to the DT via L6, the pod defaults to "combo" out, which make the DI's on the POD sound horrible. And setting it to anything other than "combo" makes the DT sound crappy. So a big "-1" on that recommendation. The hate is beginning to percolate...

"the Master Vol on the DT25 does not control DI at all. The DI is controlled by the output of the modeling amps used on the POD."

Is this referring to using the DT25 in LVM or normal mode? Or both? I spent a little time messing around with this over the weekend, and it certainly seemed to me that the DT25's master volume controlled the volume of the DI.

Yeah, my Dream Rig is sitting right here, and In LVM, in standby, listening to the DT D.I., I can totally control the D.I.'s output with the Master Volume of the DT. And the master volume of the POD. So I'm very confused about that.